1. Field of the Invention
The present invention relates to a device for establishing admittance and transport of cargo to and from an above ground level wind turbine construction and comprising a part that can be raised and lowered and/or lifted relative to the wind turbine construction, said part comprising at least two synchronically driven winches with cables/wires located at ground level, and a number snatch blocks according to the numbers of winches to be attached to a part of the wind turbine construction above ground level, a number of travelling crabs according to the numbers of winches, the travelling crabs comprising at least a first upper wheel and a second lower wheel.
2. Description of Related Art
The need to be able to perform efficient and swift inspection of blades on wind turbines, or to be able to transport relatively heavy cargo from ground level or cargo arranged on lorries at ground level to the nacelle on wind turbines, in an relatively easy manner, has in recent years increased with the number of electricity producing wind turbines. Building of wind turbines having en increased production capacity creates the need for an increasing blade length on the wind turbines, with a resulting need for towers that are correspondingly higher.
Sometimes replacement of parts in the nacelle is needed in connection with the performance of maintenance work and which entails the need for lifting relatively heavy items (28-30 tons) from ground level to the nacelle, which can be located more than 100 m above ground level for larger wind turbines. Lifting of such large and heavy loads leads to the need for large, ground level, mobile crane units which are relatively expensive, whereby the costs of maintenance and repair work will be relatively large. Furthermore, the use of mobile crane units is not optimal because the length of the extension arm (pole) leads to some instability during lifting of said heavy items.
However, to compensate for this, there are known cranes which are hoisted up from ground level and are attached in special furnished anchorage facilities on the lower side of the nacelle, whereby the handling of heavy objects is eased considerably. However, such cranes leave the task of transporting heavy objects from a ground level to a level within the reach of the said cranes anchored in the nacelle.
From International Patent Application Publication WO 2006/053554 A2, a device is known for use in mounting and dismounting wind turbine blades comprising at least one guide element extended between the nacelle and ground level and at least one suspended carrying device in a guide connected with a winch, for lifting a part of the wind turbine blade during the transport thereof between ground level and the mounting location on the shaft of the wind turbine, and at least one length adjustable backstay between the carrying device and the wind turbine blade. Thus, here, a guide, typically a steel wire, is used which guides the carrying device, as well as a common winch for performing the lifting of the wind turbine blade. The device is not suited for use in connection with inspection of blades mounted on a wind turbine.
In International Patent Application Publication WO 2005/064152 A2, a device is known for use for inspection of, e.g., blades on a wind turbine, comprising an endless frame with a guide arrangement suited for displacement along the surfaces of a wind turbine blade, the frame comprising a rail in which a gondola for inspection workers is displaceably suspended along the rail. The frame is displaced along the longitudinal axis of the wind turbine blade by a hoisting arrangement which is attached to the nacelle of the wind turbine or the shaft for a relevant wind turbine blade. This device is not suited for lifting heavy cargo, such as wind turbine blades, gearboxes for wind turbines, etc., but is solely suited for use in connection with manual inspection of wind turbine lades.